A method and system for calculating CT angiography parameters

Abstract

The present invention relates to a method and system for calculating CT angiography parameters. The method includes: based on the time-density curve of the region of interest obtained from the contrast agent bolus pre-test, and based on the theory that for the formal scan, if the contrast agent is continuously injected at the same flow rate as in the bolus pre-test, the concentration of the contrast agent at a certain position in the blood vessel will exhibit the same CT value rising rate and falling rate as in the small-dose test. By sampling points in the rising and falling segments of the time-density curve to calculate the CT value rising rate and falling rate, and combining the CT values and times of the sampled points and the CT values and times of the peak points, the delay time and contrast agent dosage required to maintain above the expected CT value during the formal scan time of the region of interest are calculated. The system includes a sampling unit and a calculation unit. The present invention can achieve CT angiography with controllable image quality and expected scanning timing, be widely used, be computer-automated, be convenient to operate, and be safe and efficient for single or multiple vascular phases.

Description

Technical Field

[0001] The present invention relates to the technical field of medical diagnosis, and specifically, to a method and system for calculating CT angiography parameters. Background Art

[0002] CT angiography (CTA) has always been an important examination method for diagnosing vascular diseases and has been widely used for many years. When the main body of the contrast agent flows along with the blood through the area of the blood vessels to be examined, exposure scanning is performed to obtain tomographic images of the target blood vessels filled with the contrast agent, and then three-dimensional post-processing is carried out to provide medical images and post-processed images of the blood vessels of the examined human body. After years of application of the current threshold method and low-dose CT angiography technology, there are already multiple contrast agent schemes suitable for CT angiography of different human blood vessels to meet the needs of clinical diagnosis, but there are still many defects.

[0003] Due to the mechanical nature of the triggering condition of the threshold method CT angiography examination, it is required that the contrast agent has a higher flow rate and a larger dosage to ensure the success of the CT angiography examination. For examinees with different blood flow velocities, especially patients with a larger body weight and a higher BMI, the problem of unstable vascular enhancement in the images has always been difficult to solve well. Too fast a flow rate often causes blood vessel rupture and contrast agent extravasation. When encountering patients with cardiopulmonary vascular diseases such as pulmonary hypertension or heart failure, the examination often fails because the blood flow of the patient is too slow and the contrast agent cannot fill the blood vessels to be examined. Taking cardiac coronary CTA as an example, Japan, the United States and other countries have successively issued technical specification guidelines for examinations. Based on the international guidelines, Chinese radiology experts launched the latest "Chinese Guidelines for the Standardized Application of Cardiac Coronary CT Angiography Technology" in 2017 based on the iodine flow rate suitable for the domestic situation, and carried out a detailed classification of the pairing of iodine flow rate and body weight, and also provided corresponding guidance on the dosage of the contrast agent. However, due to the limitations of the rationality of iodine flow rate conversion, the safety problems of the contrast agent scheme caused by high flow rates, and the problem that the CT value of vascular enhancement caused by excessive contrast agent is often unstable and exceeds the applicable range of the CT value of the diagnostic image, it is still difficult to solve well at the technical level. The registration relationship between image quality and the contrast agent scheme still needs to be studied and tackled.

[0004] The contrast agent bolus pre - test method for CT angiography (also known as the small - dose CT angiography technique) can theoretically obtain a more accurate delay time than the threshold method based on the time - density curve (TDC) obtained from small - dose tests, so as to better grasp the time phase and image quality of CT angiography. However, in practical applications, due to the dependence on experience and relatively general calculation methods, coupled with the unstable flow rate caused by the pressure change of the contrast agent high - pressure syringe, the problems of image quality and deviation of the contrast agent scheme are not significantly improved compared with the threshold method. In addition, the contrast agent dosage is equivalent to or even more than that of the threshold method, and the operation is cumbersome and inefficient, so it has not been well popularized and applied at present.

[0005] In terms of how to determine ideal CT angiography parameters to obtain higher - quality images, some methods have been reported in the prior art. For example, patent document CN110772275A discloses a CT scanning method based on ultrasound. The method includes the following steps: obtaining blood flow information of the object to be measured through an ultrasound device; determining a scanning plan for the target scanning part according to the blood flow information; and performing CT scanning on the target part of the object to be measured based on the scanning plan. The scanning plan includes at least one of the delay time, the monitoring part, the contrast agent dosage of the CT contrast agent, and the injection speed of the CT contrast agent. The beneficial effect of this technical solution is that the blood flow information measured by the ultrasound device provides a data basis for the CT scanning plan, solves the problem of high radiation dose and contrast agent dosage in the existing CT scanning process, and realizes accurate CT scanning of the target part of the object to be measured under the condition of using standard - level radiation dose and contrast agent dosage. Patent document CN111568459A discloses a method for determining the scanning delay time of CT pulmonary artery imaging scanning. Specifically, the contrast agent test method is adopted. In the test stage, in the main pulmonary artery and the same - layer pulmonary vein, circular ROIs of corresponding sizes are set at the same time to obtain the pulmonary artery - vein enhancement time - density hyperbola. The time of the hyperbola intersection point is used as TCROSS, the scanning duration is used as TSD, and the scanning delay time TDELAY is calculated through the difference between TCROSS and TSD. Its beneficial effect lies in that: performing exposure scanning according to the scanning delay time calculated by this method can obtain high - quality pulmonary artery enhancement images, which can not only accurately collect the enhanced pulmonary artery, reduce the visualization of the accompanying pulmonary vein, but also reduce the usage amount of iodine contrast agent, reduce the iodine load of the patient, and avoid the ray - hardening beam artifact caused by the concentration of iodine contrast agent in the injection - side subclavian vein and superior vena cava.

[0006] However, at present, there is no method as described in the present application that can quickly, accurately, and automatically determine the CT angiography scanning delay time and contrast agent dosage, obtain high - quality images, reduce the contrast agent dosage, improve the utilization rate of the contrast agent, and reduce the dependence of the CT angiography effect on the experience of operators. Summary of the Invention

[0007] The purpose of the present invention is to provide a method for calculating CT angiography parameters in view of the deficiencies in the prior art.

[0008] Yet another object of the present invention is to provide a system for calculating CT angiography parameters.

[0009] Another object of the present invention is to provide a CT scanning system.

[0010] In order to achieve the above first purpose, the technical solution adopted by the present invention is:

[0011] A method for calculating CT angiography parameters includes: using a time-density curve of a region of interest (ROI) obtained from a contrast agent bolus pre-test, and based on the theory that, for a formal scan, if the contrast agent is continuously injected at the same flow rate as in the bolus pre-test, the concentration of the contrast agent at a certain location in the blood vessel will exhibit a CT value rise and fall rate consistent with that during a small-dose test; calculating the CT value rise and fall rates by sampling points in the rising and falling segments of the time-density curve; and combining the CT values and times of the sampled points with the CT value and time of the peak point to calculate the delay time and contrast agent dosage required for the formal scan of the ROI.

[0012] As a preferred example, when sampling points in the rising and falling sections of the time density curve to calculate the CT value rising and falling rates, at least two points are sampled in the rising section and at least two points are sampled in the falling section.

[0013] As another preferred embodiment, the delay time and contrast agent dosage required for the formal scan are calculated using the following method and formula:

[0014] T D =T 预延 -Δt D *+T TP +(CT D *-CT TP ) / K1,

[0015] V 正式 =V 试验 +Q×Δt, where Δt=Δt 保底* +Δt 加持 , Δt 保底* =T D保底* -T TP , Δt 加持 =[CT E* -CT D* -K2×(T s -Δt D *)] / (K1-K2), T D保底* =T TP +(CT D* -CTTP ) / K1;

[0016] The meanings of the symbols in the above formula are as follows:

[0017]

[0018] As another preferred example, according to the type to which the target blood vessel belongs:

[0019] Type I: CT angiography that is not easily interfered with by the display of the next-level blood vessels for diagnosis,

[0020] Type II: CT angiography that is easily interfered with by the display of the next-level blood vessels for diagnosis,

[0021] Type III: Staged combined CT angiography;

[0022] Use different methods and formulas to calculate the delay time and contrast agent dosage required for the formal scan:

[0023] When the target blood vessel is of Type I, then T D = T 预延 -Δt D * + T TP + (CT D * - CT TP ) / K1, V 正式 = V 试验 + Q×Δt, where Δt = Δt 保底* + Δt 加持 Δt 保底* = T D保底* - T TP Δt 加持 = [CT E* - CT D* - K2×(T s - Δt D *)] / (K1 - K2), T D保底* = T TP + (CT D* - CT TP ) / K1;

[0024] When the target blood vessel is of Type II, then calculate the result of the monitoring and discrimination formula CT D(K1)* = CT TP + K1×(T* - Δt D * - T TP ), and compare it with the value of CT D *. If CT D(K1)* ≤ CT D *, then T D = T 预延 - Δt D * + TTP +(CT D *-CT TP ) / K1, V 正式 = V 试验 + Q × Δt, where Δt = Δt 保底* + Δt 加持 , Δt 保底* = T D保底* - T TP , Δt 加持 =[CT E* - CT D* - K2 × (T s - Δt D *)] / (K1 - K2), T D保底* = T TP +(CT D* - CT TP ) / K1; If CT D(K1)* > CT D *, then T D = T 预延 + T *- Δt D *, V 正式 = V 试验 + Q × Δt, where Δt =[CT E – CT TP – K2 × (T *- Δt D *+ T S - T TP )] / (K1 - K2);

[0025] When the target blood vessel is of Class III, calculate the result of the monitoring and discrimination formula CT D(K1)强制N * = CT TPN + K 1N × (T D强制N *- Δt DN *- T TPN ) and compare it with the value of CT DN *. If CT D(K1)强制N *≤ CT DN *, select the alternative delay time and contrast agent dosage calculated based on the CT angiography of its own type (Class I or Class II) at this Nth stage as the calculation result of its corresponding classification; If CT D(K1)强制N * > CT DN *, select the mandatory minimum delay time T D强制 as its delay time. At this time, the alternative dosage calculation formula for the contrast agent at this stage is as follows, and the result is used as a reference alternative. Finally, take the maximum value of each stage: Δt N =[CT EN – CT TPN – K2N ×(T N *-Δt DN *+T SN -T TPN )] / (K 1N -K 2N ), V 正式N =V 试验 +Q×Δt N , and finally take V of each period 正式N The maximum value was used as the final formal contrast agent dosage for combined CT angiography;

[0026] The meaning of each symbol in the above formula is:

[0027]

[0028]

[0029] To achieve the above second purpose, the technical solution adopted by the present invention is:

[0030] A system for calculating CT angiography parameters, comprising:

[0031] A point sampling unit is used to collect a peak point, at least one point on the rising segment, and at least one point on the falling segment from the TDC curve of the bolus injection pre-test, and obtain the CT value and time corresponding to each point;

[0032] The calculation unit is used to calculate the delay time and contrast agent dosage required for the formal scan based on the parameters collected by the sampling unit and the theory that for the formal scan, if the contrast agent is continuously injected at the same flow rate as the bolus injection pre-test, the concentration of the contrast agent at a certain position of the blood vessel will show an average CT value increase rate and decrease rate consistent with that in the small-dose test.

[0033] As a preferred example, the point sampling unit samples at least two points on the ascending section and at least two points on the descending section.

[0034] As another preferred embodiment, the calculation unit calculates the delay time and contrast agent dosage required for the formal scan according to the following method and formula:

[0035] T D =T 预延 -Δt D *+T TP +(CT D *-CT TP ) / K1,

[0036] V 正式 =V 试验 +Q×Δt, where Δt=Δt 保底* +Δt 加持, Δt 保底* = T D保底* - T TP , Δt 加持 = [CT E* - CT D* - K2×(T s - Δt D *)] / (K1 - K2), T D保底* = T TP +(CT D* - CT TP ) / K1;

[0037] The definitions of the symbols in the above formulas are as follows:

[0038]

[0039]

[0040] As another preferred example, the computing system further includes a blood vessel type selection unit for selecting and determining the type of the target blood vessel, and the type of the target blood vessel includes:

[0041] Type I: CT angiography that is not easily interfered with by the display of the next-level blood vessels for diagnosis,

[0042] Type II: CT angiography that is easily interfered with by the display of the next-level blood vessels for diagnosis,

[0043] Type III: Staged combined CT angiography;

[0044] The blood vessel type selection unit is further connected to the computing unit and sends an instruction to the computing unit to make the computing unit calculate the delay time and contrast agent dosage required for the formal scan according to the type of the target blood vessel by using the corresponding method and formula:

[0045] When the target blood vessel is of Type I, the delay time and contrast agent dosage required for the formal scan are calculated by the following method and formula: T D = T 预延 - Δt D *+ T TP +(CT D *- CT TP ) / K1, V 正式 = V 试验 + Q×Δt, where Δt = Δt 保底* + Δt 加持 , Δt 保底* = T D保底* - T TP , Δt 加持 = [CT E* - CT D* - K2×(Ts -Δt D *)] / (K1 - K2), T D保底* = T TP +(CT D* - CT TP ) / K1;

[0046] When the target blood vessel is of type II, the delay time and contrast agent dosage required for formal scanning are calculated by the following method and formula: Calculate the monitoring and discrimination formula for type II CT angiography CT D(K1)* = CT TP + K1×(T* - Δt D * - T TP ). Compare the result with the value of CT D *. If CT D(K1)* ≤ CT D *, then T D = T 预延 - Δt D * + T TP +(CT D * - CT TP ) / K1, V 正式 = V 试验 + Q×Δt, where Δt = Δt 保底* + Δt 加持 , Δt 保底* = T D保底* - T TP , Δt 加持 = [CT E* - CT D* - K2×(T s - Δt D *)] / (K1 - K2), T D保底* = T TP +(CT D* - CT TP ) / K1; If CT D(K1)* > CT D *, then T D = T 预延 + T* - Δt D *, V 正式 = V 试验 + Q×Δt, where Δt = [CT E – CT TP – K2×(T* - Δt D * + T S - T TP )] / (K1 - K2);

[0047] When the target blood vessel is of Class III, the delay time and contrast agent dosage required for the formal scan are calculated by the following method and formula: Calculate the monitoring and discrimination formula for the delayed scans of each phase of Class III CT angiography CT D(K1)强制N * = CT TPN + K 1N × (T D强制N * - Δt DN * - T TPN ), and compare the result with the value of CT DN *. If CT D(K1)强制N * ≤ CT DN *, select the delay time and contrast agent dosage alternative determined by calculating the corresponding classification situation of the self-type (Type I or Type II) of the Nth-phase CT angiography as the calculation result of its corresponding classification; if CT D(K1)强制N * > CT DN *, select the mandatory shortest delay time T D强制 of the Nth-phase CT angiography as its delay time. At this time, the calculation formula for the contrast agent alternative dosage of this phase is as follows, and the result is used as a reference alternative, and finally the maximum value of each phase is taken: Δt N = [CT EN – CT TPN – K 2N × (T N * - Δt DN * + T SN - T TPN )] / (K 1N - K 2N ), V 正式N = V 试验 + Q × Δt N , and finally select the maximum value of V 正式N of each phase as the final combined CT angiography formal contrast agent dosage;

[0048] The meanings of the symbols in the above formula are as follows:

[0049]

[0050]

[0051] More preferably, the Type I includes cerebral venous CTV, carotid CTA, coronary CTA, thoracic and abdominal CTA, lower extremity arterial CTA, superior mesenteric artery CTA, and hepatic portal vein CTV; the Type II includes cerebral arterial CTA and pulmonary artery CTA.

[0052] To achieve the above third object, the technical solution adopted by the present invention is:

[0053] A CT scanning system, comprising:

[0054] A CT scanning device for obtaining CT scan images;

[0055] A CT contrast agent for enhancing the display of CT scan images of target blood vessels;

[0056] A processor for executing the method for calculating CT angiography parameters described above.

[0057] The advantages of the present invention are as follows:

[0058] 1. The inventors of the present application observed and analyzed in clinical work that when a sufficient amount of contrast agent is used for bolus pre - test and the positioning of the region of interest in the blood vessels at the monitoring level is ideal, the obtained time - density curve shows good linearity. That is, the growth rate measured at each sampling point of the CT value from the slow - growth stage to before the peak, and the reduction rate at each point from the peak to before the slow - decline stage are basically stable. The ascending and descending segments of the curve are basically distributed in a linear function. The ascending segment is the process in which the concentration of the main body of the contrast agent bolus gradually increases with time as monitored by the pre - test monitoring point when it passes through the monitoring point position, and the descending segment is the process of pushing saline continuously until the injection stops after stopping the injection of the contrast agent. Therefore, the average growth rate and average decline rate of the CT value with inferential significance can be calculated by sampling within these two segments. Further, through the simulated linear function, the delay time and the dosage of the contrast agent for the formal scan that can obtain the expected image effect can be accurately calculated. The present invention helps to: formulate personalized contrast agent plans for examinees with different blood flow conditions through small - dose contrast agent bolus pre - test; reduce the health hazards and allergy risks to the examinees caused by excessive contrast agent dosage, provide a reference for realizing a contrast agent plan with lower flow rate, less dosage and higher safety; maximize the utilization rate of the contrast agent; and minimize the dependence on the experience of medical staff operating the equipment for CT angiography using the small - dose test method to the greatest extent.

[0059] 2. The computing system provided by the present invention can realize fully automated / semi - automated small - dose test method CT angiography, greatly improve the efficiency and success rate of CT angiography using the small - dose method, achieve safer and more accurate personalized angiography, obtain stable expected image quality, and achieve precise images and accurate diagnosis.

[0060] 3. The present application provides a detailed calculation method. According to the anatomical characteristics of different target blood vessels, the target blood vessels are divided into three types, and more scientific and reasonable calculation methods are provided for different types of target blood vessels, which helps to further improve the image quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] Figure 1 : Obtaining the time - density curve of the region of interest of the blood vessel at the monitoring level.

[0062] Figure 2 : Figure 1Zoomed in view of the time density curve in .

[0063] Figure 3 :When the contrast agent bolus pre-test dose is sufficient, a good linear ascending segment and a linear descending segment will be formed.

[0064] Figure 4 : Under ideal conditions, the rise and fall rates of low-dose testing are the same as those of CTA scanning.

[0065] Figure 5 Examples of sampling points: A. Manually select representative points on a linearly ascending segment; B. Manually select representative points on a linearly descending segment; C. Manually collect peak point information.

[0066] Figure 6 : Category I CT angiography: TDC curves of monitoring points in coronary CTA.

[0067] Figure 7 : Analytical diagram of TDC function estimation for type I CT angiography.

[0068] Figure 8 : TDC curve of the monitoring point of the pulmonary artery CTA contrast agent bolus injection pre-test. The sampling point in the figure is the phase suppression time node T* of the pulmonary artery CTA monitoring point. T* is the time node when the left atrial CT value reaches 141HU. This is used as the triggering time to ensure the filling of the pulmonary artery and to suppress the display of the pulmonary vein as much as possible, avoiding the formation of "pulmonary vein contamination" on the image that causes visual interference to the diagnosis.

[0069] Figure 9 : Analytical diagram of the TDC curve bottom-line solution function for case 1 of type II CT angiography.

[0070] Figure 10 : Analytical diagram of the TDC curve phase suppression scheme function calculation for case II of type II CT angiography.

[0071] Figure 11 : Analysis diagram of TDC curve function calculation of type III CT angiography (pulmonary artery + pulmonary vein left atrium).

[0072] Figures 12 - 17 : Point map of cerebral artery CTA+cerebral vein CTV combined scanning.

[0073] Figure 18 : Table of formulas for calculating delay time and contrast agent dosage for type I CT angiography.

[0074] Figure 19 : Table of formulas for calculating delay time and contrast agent dosage for type II CT angiography.

[0075] Figure 20: Table of formulas for calculating the delay time and contrast agent dosage of Class III CT angiography (combined angiography).

[0076] Figures 21 - 24 : Sampling situations of monitoring levels, monitoring points and TDC curves in Case 1 of Example 4. Figure 21 : T* = 13.84 seconds, CT* = 74 HU; Figure 22 : T1 = 7.19 seconds, CT1 = 136 HU; Figure 23 : T TP = 9.41 seconds, CT TP = 218 HU; Figure 24 : T2 = 12.73 seconds, CT2 = 149 HU.

[0077] Figure 25 : Table of cerebral artery CTA formulas for Case 1 in Example 4, Plan 1 for Class II situation.

[0078] Figure 26 : Test results of the monitoring level position during the formal scan in Case 1 of Example 4. The CT enhancement value of the left internal carotid artery is 406 HU, the CT value of the left external carotid artery is 401 HU, and the left internal jugular vein is 121 HU.

[0079] Figure 27 : Formal scan images, VRT and MIP three-dimensional reconstruction results after fine-tuning the default window value in Case 1 of Example 4. A. Default window value VRT (anteroposterior view); B. Default window value MIP (anteroposterior view); C. Default window value VRT (left anterior oblique view); D. Default window value MIP (left anterior oblique view); E. Severe stenosis at the opening of the right internal carotid artery; F. Lack of blood supply in the M3 segment of the right middle cerebral artery.

[0080] Figure 28 : DSA examination results in Case 1 of Example 4. A. Anteroposterior view of DSA examination shows severe stenosis at the opening of the right internal carotid artery; B. Lateral view of DSA examination shows severe stenosis at the opening of the right internal carotid artery; C. DSA examination shows multiple stenoses in the left vertebral artery.

[0081] Figures 29 - 31 : Sampling situations of monitoring levels, monitoring points and TDC curves in Case 2 of Example 4. Figure 29 : For the carotid artery sampling point 1, T1 = 1.66 seconds, CT1 = 125 HU; Figure 31 : For the carotid artery sampling point T TP = 4.97 seconds, CT TP = 325 HU; Figure 32 : For the carotid artery sampling point 2, T2 = 8.29 seconds, CT2 = 202 HU.

[0082] Figure 32 : Table of carotid artery CTA formulas for Case 2 in Example 4, Class I CT angiography.

[0083] Figure 33 : Verification of the formal scan image monitoring layer in Case 2 of Example 4, carotid artery 417 HU, left carotid artery 425 HU.

[0084] Figures 34 - 35 : Three-dimensional reconstruction effect diagrams of the default window value VRT and the appropriate window value MIP of the formal scan image in Case 2 of Example 4. Figure 34 : Three-dimensional reconstruction effect diagram of the carotid artery VRT default window value; Figure 35 : Three-dimensional reconstruction effect diagram of the carotid artery appropriate window value MIP.

[0085] Figures 36 - 39 : Monitoring levels, monitoring points and TDC curve sampling points in Case 3 of Example 4. Figure 36 : Sampling point 1, T1 = 3.87 s, CT1 = 105 HU; Figure 37 : Peak sampling point, T TP = 6.08 s, CT TP = 403 HU; Figure 38 : Sampling point 2, T2 = 7.74 s, CT2 = 199 HU; Figure 39 : Phase suppression point, T* = 7.8 s, CT* = 150 HU.

[0086] Figure 40 : Pulmonary artery CTA formula table in Case 3 of Example 4, Class II CT angiography.

[0087] Figure 41 : The measured value at the left atrium monitoring point in the monitoring level of Case 3 of Example 4 is 170 HU, the pulmonary artery trunk is 299 HU, and the area near the heart is greatly affected by the cardiac pulsation.

[0088] Figures 42 - 46 : Formal scan tomographic image and three-dimensional reconstruction effect diagram of the default window value VRT in Case 3 of Example 4. Figure 42 : The pulmonary artery of the apical segment and the pulmonary vein terminal are clearly distinguishable; Figure 43 : The pulmonary artery and the pulmonary vein are clearly distinguishable at the left atrium level; Figure 44 : Coronal reconstruction of the pulmonary artery; Figure 45 : Coronal plane (lung window) of the pulmonary artery; Figure 46 : Three-dimensional reconstruction effect diagram of the default window value VRT without any processing.

[0089] Figure 47 : Only the VRT three-dimensional reconstruction diagram and the MIP diagram with the appropriate window value after cutting in Case 3 of Example 4. A. VRT anteroposterior view; B. VRT left lateral view; C. VRT posteroanterior view; D. MIP anteroposterior view; E. MIP left lateral view; F. MIP posteroanterior view.

[0090] Figures 48 - 50: Monitoring levels, monitoring points, and TDC curve sampling points in Case 4 of Example 4. Figure 48 : Sampling point 1, T1 = 6.09 seconds, CT1 = 116.95 HU; Figure 49 : Peak sampling point, T TP = 8.3 seconds, CT TP = 212.48 HU; Figure 50 : Sampling point 2, T2 = 12.17 seconds, CT2 = 156.08 HU.

[0091] Figure 51 : Cardiac coronary CTA formula table in Case 4 of Example 4, Class I CT angiography.

[0092] Figure 52 : New iodine flow rate and velocity used in Case 4 of Example 4. Comparison of iodine flow rate, contrast agent specifications, velocity, and dosage in the Chinese Guidelines for the Standardized Application of Cardiac Coronary CT Angiography Technology (2017 Edition) with the corresponding reduced velocity using the method of the present invention for cardiac coronary CTA examination. In this case, the total amount of contrast agent for the patient is 15 ml + 47 ml, a total of 62 ml, and the dosage in the coronary guidelines is 72 ml.

[0093] Figure 53 : CT value at the monitoring level and monitoring point position in the formal scan image of Case 4 of Example 4 is 381 HU, about 120 HU lower than expected, caused by a decrease in heart rate. (Pre-test heart rate was 70 bpm, and during the formal scan it was 65 bpm).

[0094] Figure 54 : CT value measurement results in Case 4 of Example 4: ① Left main trunk: 390 HU; ② Proximal left anterior descending branch: 431 HU; ③ Distal left anterior descending branch; ④ Proximal left circumflex branch: 443 HU; ⑤ Distal left circumflex branch: 448 HU; ⑥ Proximal right coronary artery: 390 HU; ⑦ Distal right coronary artery: 388 HU.

[0095] Figure 55 : 3D post-processing effect diagram of coronary CTA in Case 4 of Example 4.

[0096] Figures 56 - 58 : Monitoring levels, monitoring points, and TDC curve sampling points in Case 5 of Example 4. Figure 56 : Sampling point 1, T1 = 4.43 seconds, CT1 = 151 HU; Figure 57 : Peak sampling point, T TP = 7.75 seconds, CT TP = 317 HU; Figure 58 : Sampling point 2, T2 = 10.52 seconds, CT2 = 219 HU.

[0097] Figure 59 : Pulmonary vein formula table in Case 5 of Example 4, Class I CT angiography.

[0098] Figure 60 : Test results of monitoring points at the monitoring level in Case 5 of Example 4. First filling: ① CT value at end-diastole is 466 HU; ② CT value at end-systole is 502 HU. Second filling: ③ CT value at end-diastole is 521 HU; ④ CT value at end-systole is 508 HU.

[0099] Figures 61 - 62 : 3D post-processing effect diagram of the formal scan image in Case 5 of Example 4. Figure 61 : VRT 3D reconstruction diagram without processing with the default window value; Figure 62 A. Fine-tune the window value, and the image of the left atrium and left atrial appendage of the pulmonary vein after cutting (75% R-R interval); Figure 62 B. Measure the size of the left atrial appendage occluder. If the cumulative amount of contrast agent injection in the two filling schemes reaches 100 ml, then the second injection of contrast agent can be omitted, and a low-KV scan can be directly performed after delaying for 45 - 60 seconds (waiting for the contrast agent injected for the first time to return to the heart through the systemic circulation). Voltage grading for single injection scheme: 120 kv for the first time and 100 kv for the second time for those over 60 kg; 100 kv for the first time and 80 kv for the second time for those under 60 kg.

[0100] Figures 63 - 65 : Monitoring level, monitoring points and TDC curve sampling points in Case 6 of Example 4. Figure 63 : Sampling point 1, T1 = 4.99 s, CT1 = 126.58 HU; Figure 64 : Peak sampling point, T TP = 7.2 s, CT TP = 191.08 HU; Figure 65 : Sampling point 2, T2 = 8.87 s, CT2 = 154.15 HU.

[0101] Figure 66 : Thoracic aorta CTA formula in Case 6 of Example 4, Class I CT angiography.

[0102] Figure 67 : CT value test of monitoring points at the monitoring level in Case 6 of Example 4: 348 HU.

[0103] Figure 68 : VRT 3D reconstruction diagram with the default window value in Case 6 of Example 4.

[0104] Figure 69 : Sheared VRT 3D reconstruction diagram in Case 6 of Example 4.

[0105] Figure 70 : Sheared MIP 3D reconstruction diagram in Case 6 of Example 4.

[0106] Figures 71 - 74 : Monitoring level, monitoring points and TDC curve sampling points in Case 7 of Example 4.Figure 71 : Sampling point 1, T1 = 7.19 seconds, CT1 = 132.07 HU; Figure 72 : Peak sampling point, T TP = 11.07 seconds, CT TP = 206.16 HU; Figure 73 : Sampling point 2, T2 = 14.93 seconds, CT2 = 166.55 HU; Figure 74 : Phase suppression sampling point, T* = 17.14 seconds, CT* = 114.55 HU.

[0107] Figure 75 : CT scanning protocol formula for pulmonary artery CTA + right atrium and ventricle diastolic & systolic end - volume index analysis in Case 7 of Example 4, Class II CT angiography.

[0108] Figures 76 - 77 : Inspection results of the formal scan tomographic image quality in Case 7 of Example 4. Figure 76 : Monitoring points in the diastolic monitoring layer: pulmonary artery trunk 494 HU, left atrium at the phase suppression node 388 HU; ​ : Monitoring points in the diastolic monitoring layer: pulmonary artery trunk 457 HU, left atrium at the phase suppression node 383 HU.

[0109] ​ : Default VRT three - dimensional reconstruction map of Case 7 in Example 4 without window value cutting: from left to right are anteroposterior view, left lateral view, and posteroanterior view.

[0110] ​ : VRT three - dimensional reconstruction map of Case 7 in Example 4 after adjusting window value cutting: from left to right are anteroposterior view, left lateral view, and posteroanterior view.

[0111] ​ : VRT three - dimensional reconstruction of right atrium and ventricle diastolic and systolic volumes in Case 7 of Example 4. ① Right atrial end - diastolic volume 288.5 cc; ② Right atrial end - systolic volume 297.8 cc; ③ Right ventricular end - diastolic volume 321.3 cc; ④ Right ventricular end - systolic volume 300.1 cc.

[0112] ​ : Monitoring layer, monitoring points and sampling points of TDC curve in Case 8 of Example 4. Sampling point 1 in the CTA phase of cerebral artery: T 1A = 3.32 seconds, CT 1A = 151 HU; Peak sampling point: T TPA = 6.09 seconds, CT TPA = 306 seconds; Sampling point 2: T 2A = 9.95 seconds, CT 2A = 189 HU; Phase suppression sampling point: T* A = 10.6 seconds, CT*A = 120 HU (reference CTV acquisition point 1); Cerebral vein CTV acquisition point 1: T 1V = 10.51 seconds, CT 1V = 114 HU; Peak acquisition point: T TPV = 14.38 seconds, CT TPV = 265 HU; Acquisition point 2: T 2V = 19.91 seconds, CT 2V = 125 HU.

[0113] ​ : Case VIII staging delay cerebral vascular CT combined scanning formula in Example 4, Class III CT angiography (Structure II + I).

[0114] ​ : CT value of the monitoring point of the right common carotid artery at the monitoring level in Case VIII of Example 4 is 483 HU, and the CT value of the right jugular vein at the phase suppression monitoring point is 114 HU.

[0115] ​ : CT value of the right jugular vein at the monitoring point of the monitoring level in Case VIII of Example 4 is 420 HU.

[0116] ​ : Default VRT effect diagrams of the anterior-posterior and left-lateral views of cerebral artery CTA in Case VIII of Example 4. [[ID=3)]]

[0117] ​ : Default VRT effect diagrams of the anterior-posterior and left-lateral views of cerebral vein CTV in Case VIII of Example 4.

[0118] ​ : Acquisition point information of the monitoring point at the monitoring level in Case IX of Example 4. Pulmonary artery phase acquisition point: ① Pulmonary trunk acquisition point 1, T 1A = 5.53 seconds, CT 1A = 217 HU; ② Pulmonary trunk peak acquisition point, T TPA = 6.63 seconds, CT TPA = 390 HU; ③ Pulmonary trunk acquisition point 2, T 2A = 9.4 seconds, CT 2A = 250 HU; ④ Left atrium acquisition point 1 / pulmonary artery phase time suppression node, T 1V / T * A = 9.4 seconds, CT 1V / CT * A = 126 HU; ⑤ Left atrium peak acquisition point, T TPV = 12.72 seconds, CT TPV = 306 HU; ⑥ Left atrium acquisition point 2, T 2V = 15.49 seconds, CT 2V = 173 HU.

[0119] ​ : Formula table after substituting each parameter of the CT pre-operative evaluation plan for the one-stop operation of delayed staged cardiovascular radiofrequency ablation and left atrial appendage occlusion in Case Nine of Example 4.

[0120] ​ : Inspection results of the formal scan images in Case Nine of Example 4. ① Inspection of the CT values of the monitoring points in the monitoring layer of the formal pulmonary artery phase image, with the pulmonary artery trunk at 466 HU and the left atrial phase suppression point at 189 HU; the left atrium was scanned for the first time with forced delay at the end of the pulmonary artery phase scan, ② the CT value in diastole was 303 HU, ③ the CT value in systole was 322 HU; after a one-minute delay, the left atrium was filled separately for the second time, ④ the CT value in diastole was 376 HU, ⑤ the CT value in systole was 379 HU.

[0121] ​ : Each three-dimensional post-processing effect diagram in Case Nine of Example 4. ① Unprocessed pulmonary artery phase VRT three-dimensional post-processing diagram with default window value; ② VRT three-dimensional post-processing effect diagram in the anteroposterior position after only adjusting the window value, which can be used to observe the situation of the persistent left superior vena cava and the coronary sinus of the heart; ③ right lateral VRT of the pulmonary artery phase; ④ posteroanterior VRT of the pulmonary artery; ⑤ left atrial appendage VRT at the end of diastole of the left atrium; ⑥ posteroanterior position of the left atrium, VRT of the pulmonary vein ostium position.

[0122] ​ : Measurement data of the left atrial appendage occluder in Case Nine of Example 4. ​ : Measured spatial angle of the left atrial appendage occluder; ​ : Measured dimension data of the left atrial appendage occluder.

[0123] ​ : Sampling point information of the monitoring points in the monitoring layer in Case Ten of Example 4. ① Sampling point 1 in the first phase: T 11 = 6.1 seconds, CT 11 = 176.87 HU; ② Peak sampling point in the first phase: T TP1 = 7.6 seconds, CT TP1 = 285.93 HU; ③ Sampling point 2 in the first phase: T 21 = 10.52 seconds, CT 21 = 223.84 HU; ④ Phase suppression node in the first phase: T*1 = 11.07 seconds, CT*1 = 105.07 HU; ⑤ Sampling point 1 in the second phase: T 12 = 14.95 seconds, CT 12 = 160.12 HU; ⑥ Peak sampling point in the second phase: T TP2 = 16.61 seconds, CT TP2 = 204.58 HU; ⑦ Sampling point 2 in the second phase: T 22 = 21.59 seconds, CT 22 = 139.05 HU.

[0124] ​ : The whole body CT angiography protocol for Case 10 in Example 4, Class III CT angiography, Structure II+I. The delay time for the first phase is 13.1 seconds for Class II cases, and the delay time for the second phase is the normal delay time of 29.6 seconds. The contrast agent dosage is 83 ml + 30 ml of normal saline. If left atrial appendage analysis is required, this protocol can be followed by a 60-second delay and a follow-up scan in the case of no further injection of the contrast agent to evaluate the filling of the left atrial appendage.

[0125] ​ : The image quality inspection results for Case 10 in Example 4. First phase: ① The CT value at the monitoring point of the pulmonary artery trunk during systole is 397 HU, and the CT value at the left atrial phase suppression node is 78 HU; ② The CT value at the monitoring point of the pulmonary artery trunk during diastole is 358 HU, and the CT value at the left atrial phase suppression node is 86 HU; Second phase: ③ The CT value at the monitoring point of the left atrium during diastole is 381 HU; ④ The CT value at the monitoring point of the left atrium during systole is 428 HU; ⑤ The CT value at the position of the right coronary artery opening is 429 HU; ⑥ The left main trunk is 403 HU, the proximal left anterior descending is 400 HU, and the left circumflex branch is 423 HU.

[0126] ​ : The three-dimensional reconstruction effect diagram of part of Case 10 in Example 4. ​ : The three-dimensional post-processing diagram of the pulmonary artery and the right atrium and ventricle, which can perform separate pulmonary artery VRT / MIP, right atrium and ventricle diastolic and systolic volume analysis; ​ : The three-dimensional post-processing effect diagram of the left atrial part of the pulmonary veins, which can perform separate pulmonary vein VRT / MIP, left atrium and ventricle diastolic and systolic volume analysis, radiofrequency ablation and left atrial appendage occlusion analysis and evaluation, coronary artery CTA post-processing, and thoracic aorta CTA analysis and processing; ​ : The estimated measurement angle and size of the left atrial appendage occluder. Detailed implementation manners

[0127] The following will make a detailed description of the specific implementation manners provided by the present invention in conjunction with the accompanying drawings.

[0128] Example 1

[0129] The inventors of the present application found in the clinical trials based on the low-dose CT angiography technology that: when a contrast agent bolus pre-test is performed with a sufficient amount of contrast agent (for example, a contrast agent with a specification of 350 mgI / ml, injecting 15-20 ml of contrast agent + 20-30 ml of normal saline at the same flow rate), when the positioning of the region of interest in the blood vessel at the monitoring level is ideal, the obtained time-density curve (TDC) will show a good linearity ( ​ ), that is, the growth rate measured at each sampling point of the CT value from the slow growth section to before the peak, and the decrease rate at each point from the peak to before the slow decline section are basically stable. The ascending and descending sections of the curve are basically distributed in a linear function, and the average growth rate and average decline rate of the CT value with inferential significance can be calculated by sampling points within these two sections.​ )。Combined with this discovery, based on the pharmacokinetic characteristics of the contrast agent, it is analyzed that when a large amount of contrast agent is continuously injected at the same flow rate during the formal scan, the average CT value increase rate and decrease rate of the contrast agent will be basically the same as those during the small-dose test before the systemic circulation time arrives. ​ )。Through linear function calculation, the contrast agent concentration in the region of interest at this moment can be deduced to reach the initial expected CT value, as well as the delay time and dosage of the contrast agent when the contrast agent concentration at the end time node TE of the scan still remains above the CT expected value at the end moment, so as to determine the contrast agent scheme that conforms to the pharmacokinetic characteristics of the subject (the pharmacokinetic contrast agent scheme described in this article, that is, within the scan time, the contrast agent enhancement value in the region of interest is speculated to be maintained above the respective expected CT values at the start and end of the scan through linear function calculation). The average CT value increase rate and decrease rate can be obtained by taking a representative TDC point in each of the linear ascending and descending segments, and calculating based on the time node and CT value information of the peak point (the point-taking method is exemplified as ​ )。Moreover, multiple points can be collected for automated calculation to more accurately calculate the average CT value increase rate and decrease rate of the linear ascending and descending segments.

[0130] Based on this, the present invention provides a method for calculating CT angiography parameters, including the following steps: According to the time-density curve of the region of interest obtained from the contrast agent bolus pretest, based on the theory that for the formal scan, if the contrast agent is continuously injected at the same flow rate as in the contrast agent bolus pretest, the concentration of the contrast agent at a certain position in the blood vessel will show the same average CT value increase rate and decrease rate as those during the small-dose test. By sampling points in the ascending and descending segments of the time-density curve and based on the CT value, time of the sampled points, and the CT value and time of the peak point, the delay time and contrast agent dosage required for the formal scan of the region of interest are calculated.

[0131] Next, the method for calculating CT angiography parameters provided by the present invention will be introduced in detail. Since different blood vessels have different anatomical characteristics, in order to obtain better angiographic images, more preferably, according to the anatomical characteristics of the blood vessels, we divide CT angiography into CT angiography that is not easily interfered with by the display of the next-level blood vessels for diagnosis, CT angiography that is easily interfered with by the display of the next-level blood vessels for diagnosis, and combined CT angiography in the form of delayed staging:

[0132] 1. CT angiography that is not easily interfered with by the display of the next-level blood vessels for diagnosis, hereinafter collectively referred to as type I CT angiography. Examples: cerebral venous CTV, carotid CTA, coronary CTA, thoracic and abdominal CTA, lower extremity arterial CTA, superior mesenteric artery CTA, hepatic portal vein CTV, etc.

[0133] 2. CT angiography that is easily interfered with by the display of the next-level blood vessels is hereinafter collectively referred to as Class II CT angiography. Examples: cerebral artery CTA, pulmonary artery CTA, etc.

[0134] CT angiography categories not listed above can be classified as Class I or Class II according to the classification principle by themselves.

[0135] Note: The phase requirement means the requirement to suppress the imaging of the next-level blood vessels in the direction of the blood vessels and avoid the imaging of the next-level blood vessel system. For CT angiography images with good phase suppression, the examined blood vessels and branches that are sufficiently enhanced can be visually distinguished and judged, and the blood vessels and branches of the next level that are not significantly enhanced by the contrast agent can be distinguished. For example, when performing pulmonary artery CTA, it is necessary to suppress the imaging of the pulmonary vein system, and when performing cerebral artery CTA, it is necessary to suppress the imaging of the cerebral veins. Accurate timing will make image diagnosis more efficient and accurate, and three-dimensional post-processing more convenient, efficient and of high quality.

[0136] 3. Staged combined CT angiography is hereinafter collectively referred to as Class III CT angiography, that is, during formal CT angiography, a contrast agent is injected once, and two or more different CT angiography examinations are sorted according to the delay time in a staged and delayed manner, and then scanned in sequence.

[0137] For the above three types of CT angiography, the calculation methods of CT angiography parameters are different. Using the corresponding methods for calculation will help to further improve the quality of the scanned images. The calculation methods of the parameters of the three types of CT angiography are introduced separately as follows. The symbols involved and their definitions are shown in Table 1.

[0138] Table 1 Technical parameters and definitions

[0139]

[0140]

[0141]

[0142] 1. Calculation method of Class I CT angiography parameters

[0143] 1.1 Overview of Class I scheme

[0144] Due to the characteristics of vascular anatomy, CT angiography is less susceptible to visual interference from downstream vessels. During the period when the contrast agent fills the target vessel and its branches, the filling of the downstream vessels will not visually affect or interfere with the display of the 3D post-processing renderings of the target vessel. Alternatively, the interfering display time of the downstream vessels and their branches far exceeds the sum of the delay and scanning time during normal scanning of the target vascular system, thus preventing visual interference during 3D post-processing of the CT images. Although CT angiography of such vessels requires minimal time phase, it is often affected by factors such as the stability of the high-pressure injector flow rate, changes in blood volume, blood viscosity, blood flow velocity, pulmonary artery pressure, heart rate, and heart failure that cause changes in human hemodynamics, often affecting the examination results. The CT enhancement value of the examined vessel image is difficult to control, and in extreme cases (such as patients with severe pulmonary hypertension or severe heart failure), the scan often fails.

[0145] To address this issue, the present invention applies a phase suppression condition to the examined vessels. The principle is as follows: By applying a linear function to the TDC curve of a pre-test contrast agent bolus injection, the CT enhancement value (contrast agent concentration) of the examined vessels is maintained above the desired CT enhancement value throughout the exposure scan. This, combined with conventional scanning and reconstruction parameter scanning protocols, achieves CT vascular scans that meet the desired image quality, resulting in excellent vascular visualization.

[0146] The contrast agent bolus pre-test monitoring points and TDC curve and function analysis diagram are shown in ​ 、 ​ .

[0147] 1.2 Analysis of the calculation of formal scan parameters based on the linear function of the bolus pre-test TDC in type I CT angiography

[0148] In a constant-flow contrast agent injection scheme, the ideal solution for controlling image quality is to trigger the exposure scan when the contrast agent concentration in the target vessel reaches the desired starting value during formal CT angiography. At the end of the scan, the contrast agent concentration just drops back to the concentration value at the desired scan end time. This maximizes the control of the CT enhancement value in the examined vessel in the image, keeping it within an acceptable range as much as possible, while maximizing the utilization of the contrast agent. Therefore, the phase suppression time node T* of Class I is T D保底* , CT*=CT D保底* =CT D* The instantaneous phase suppression is the reference delay for scanning when the CT value of the monitoring point of the tested blood vessel reaches the expected value of the scan start. Here, a single-phase contrast agent with a constant flow rate is taken as an example. ​ Linear function graph, the calculation formula derivation process is as follows:

[0149] T D =T预延 +T D *-------------------------------- Formula 1

[0150] T D * = T D保底* -Δt D *-------------------------------------- Formula 2

[0151] T s = T E -T D --------------- Formula 3

[0152] T s = T E *-T D *-------------------------------------- Formula 4

[0153] K1=(CT TP -CT1) / (T TP -T1)------------------------------- Formula 5

[0154] K2=(CT2 - CT TP ) / (T2 - T TP )------------------------------ Formula 6

[0155] K2=(CT TPS -CT E* ) / (T TPS -T E *)----------------------- Formula 7

[0156] T D保底* = T TP +(CT D* -CT TP ) / K1------------------ Formula 8

[0157] Δt 保底* = T D保底* -T TP -------------------------------- Formula 9

[0158] T TPS = T D保底* +Δt 加持-----------------------------Formula 10

[0159] CT TPS = CT D* + K1 × Δt 加持 ---------------------------Formula 11

[0160] Δt = Δt 保底* + Δt 加持 ----------------------Formula 12

[0161] V 正式 = V 试验 + Q × Δt-------------------------Formula 13

[0162] Integrating Formulas 2, 4, 8, 6, 10, and 11, we get:

[0163] Δt 加持 = [CT E* - CT D* - K2 × (T s - Δt D *)] / (K1 - K2)------------------Formula 14

[0164] Integrating Formulas 1, 2, and 8, we get the calculation formula for the delay time of type I CT angiography:

[0165] T D = T 预延 - Δt D * + T TP + (CT D * - CT TP ) / K1

[0166] Integrating Formulas 8, 9, 12, 13, and 14, we can obtain the reference dosage V of the contrast agent for formal CT angiography 正式 .

[0167] 2. Calculation method for parameters of type II CT angiography

[0168] 2.1 Overview of type II scheme

[0169] Affected by the differences in human hemodynamics, the blood flow velocity of each person is different. During scanning, it is found that when setting the phase-inhibited CT value CT* in the blood vessel at the next level of the target blood vessel in the detection layer, for example, when scanning pulmonary artery CTA, when the CT value of the pulmonary vein reaches 150 HU as the phase-inhibited CT value, the expected CT value of the pulmonary artery trunk is 400 HU. In most cases, the two cannot be taken into account at the same time, and for examinees in different situations, the time sequence of meeting the two conditions is uncertain. Internal and external factors of the human body such as the stability maintained by the flow rate of the high-pressure injector, the heart rate change during scanning, the pulmonary artery pressure value, the degree of heart failure, blood viscosity, blood flow velocity, blood volume, height, weight, and the size of the BMI index will ultimately comprehensively affect the sequence of meeting these two conditions. The same situation will also occur during the scanning process of cerebral artery CTA. This is also the reason why when CT operators use the conventional threshold method and the ordinary small-dose method to perform angiographies such as cerebral artery CTA and pulmonary artery CTA with relatively high phase requirements, they often encounter problems such as contrast agent filling defects and venous contamination, as well as difficulties in controlling the enhancement value of the blood vessels to be examined. If such CT angiography examinations are expected to achieve a high success rate, there is a relatively high threshold for on-site experience, and it is necessary to understand the relevant reports of the patients, understand the mechanism of pathological changes, and make corresponding adjustments to the contrast agent plan before completing the examination with a relatively high success rate. At present, the number of examinees in major domestic hospitals is large, and it is often impossible to provide sufficient relevant report information. The number of highly qualified CT operators is small and unevenly distributed, which greatly hinders the development of CT angiography technology and makes it difficult to achieve accurate imaging and accurate diagnosis in a general sense.

[0170] In order to achieve accurate imaging and accurate diagnosis for CT angiography with relatively high phase requirements, the present invention adopts a method of classification to deal with examinees in different situations, and on the basis of controlling the CT enhancement value of the blood vessels to be examined, takes into account the control of the phase, so as to achieve accurate imaging and accurate diagnosis.

[0171] The phase control of type II CT angiography is achieved by setting the inhibitory CT value in the blood vessel at the next level. The principles are as follows: Through the function calculation of the contrast agent bolus pretest TDC, it is the primary condition to ensure that the CT enhancement value at the TDC monitoring point position of the blood vessel to be examined and its branches reaches above the expected CT value; it is the secondary condition to make the terminals of the blood vessel to be examined and its branches fully filled with the contrast agent and inhibit the display of the blood vessel at the next level. On the premise of ensuring the image quality, the phase is controlled.

[0172] By setting the inhibitory display CT value (the CT* value at time T*) at the TDC monitoring position of the blood vessel at the next level, pre-calculate the CT value CT that the blood vessel to be examined will reach at the starting time T of the exposure scan at the TDC monitoring point position of the bolus pretest D (i.e., T D time node) D(K1)* and confirm CT D(K1)*Whether the CT value CT at the expected start time of scanning is satisfied D* , this solution is divided into two cases:

[0173] Case 1: CT D(K1)* ≤CT D* : The CT value at the official start of scanning of the monitored point of the vessel to be examined obtained by calculation will not be able to reach the expected enhancement value CT D* . To ensure that the vessel to be examined is enhanced as expected and to ensure the image quality, the original phase suppression is abandoned, and the time node T when the CT value at the monitored point of the vessel to be examined reaches the expected CT value at the start of the official scan is obtained through function calculation D保底* , and this time node is used as the delayed reference time node T D *, and the delay time T D is recalculated.

[0174] Case 2: CT D(K1)* >CT D* : The CT value at the official start of scanning of the monitored point of the vessel to be examined obtained by calculation will exceed the expected enhancement value CT D* . At this time, the T* moment can be used as the delayed reference time node T D * to calculate the delay time T D , so as to suppress the enhancement of the vessels and branches at the next level of the official scan image, achieving the dual goals of ensuring the image quality and suppressing the phase of the vessel to be examined.

[0175] Examples of the positions of the TDC monitoring points in the bolus pre-experiment are shown in ​ , and the function analysis diagrams of the two cases are shown in ​ 、 ​ .

[0176] 2.2 Analysis of calculating the official scan parameters based on the bolus pre-experiment TDC linear function in type II CT angiography

[0177] By setting a monitoring point at the phase suppression node, that is, monitoring the CT value CT reached by the vessel to be examined at the moment of the phase suppression node of the TDC curve D(K1)* , to judge which case of function analysis is suitable for the individual to be examined.

[0178] (CT D(K1)* -CT TP ) / (T*-T TP )=K1

[0179] Combined with the adjustment time Δt D * of T*:

[0180] (CT D(K1)* -CT TP ) / (T*-Δt D *-T TP )=K1

[0181] Obtain the discrimination formula for monitoring the II - type CT angiography situation:

[0182] CT D(K1)* = CT TP + K1×(T* - Δt D * - T TP )

[0183] The situation classification is as follows:

[0184] Situation 1 (guaranteed plan): CT D(K1)* ≤ CT D *;

[0185] Situation 2 (lower - level blood vessel display inhibition plan): CT D(K1)* >CT D *.

[0186] 2.2.1 Function analysis of Situation 1 (guaranteed plan):

[0187] Since the contrast agent concentration of the blood vessel under examination at the time - phase control time node T* does not meet the expected CT value CT D * expected at the start of the scan, to ensure the image quality and make the blood vessel under examination reach the expected enhancement, it is necessary to abandon the time - phase inhibition function set for the next - level blood vessel at this time, or take a larger CT value as the time - phase inhibition value CT*, and re - take T* for situation analysis.

[0188] Under normal circumstances, when abandoning the time - phase inhibition function of the next - level blood vessel, the time - phase inhibition condition becomes that the CT value of the monitoring point of the blood vessel under examination reaches the expected CT value at the start and end of the scan, that is, Situation 1 is the same as the type - I angiography plan.

[0189] Combined with Table 1 and ​ the function analysis diagram, the derivation process of the calculation formula is as follows:

[0190] T D = T 预延 + T D *------------------------------------------ Formula 1

[0191] T D * = T D保底* - Δt D *------------------------------ Formula 2

[0192] T s = T E - T D-----------------------------------Formula 3

[0193] T s =T E *-T D *----------------------Formula 4

[0194] K1=(CT TP -CT1) / (T TP -T1)-------------------------Formula 5

[0195] K2=(CT2 - CT TP ) / (T2 - T TP )------------------------Formula 6

[0196] K2=(CT E *-CT TPS ) / (T E *-T TPS )------------------------Formula 7

[0197] T D保底* =T TP +(CT D* -CT TP ) / K1-----------------------Formula 8

[0198] Δt 保底* =T D保底* -T TP --------------------------------Formula 9

[0199] T TPS =T D保底* +Δt 加持 --------------------------------Formula 10

[0200] CT TPS =CT D* +K1×Δt 加持 --------------------------Formula 11

[0201] Δt=Δt 保底* +Δt 加持 ------------------------------Formula 12

[0202] V 正式 = V 试验 + Q × Δt --------------------------- Equation 13

[0203] Integrating Equations 2, 4, 8, 6, 10, and 11 gives:

[0204] Δt 加持 = [CT E* - CT D* - K2 × (T s - Δt D *)] / (K1 - K2) --------------------------- Equation 14

[0205] Integrating Equations 1, 2, and 8 gives the formula for the formal CT angiography delay time in Case 1:

[0206] T D = T 预延 - Δt D * + T TP + (CT D * - CT TP ) / K1

[0207] Integrating Equations 8, 9, 12, 13, and 14 gives the reference contrast agent dosage V for formal CT angiography 正式 .

[0208] 2.2.2 Function analysis for Case 2 (lower - level vessel display suppression scheme):

[0209] Combined with ​ the function analysis diagram, when it is speculated that the CT value of the vessel under examination at the time - phase suppression time node exceeds the CT value at the scan start time node, i.e., CT D(K1)* > C TD *, the CT value at the scan start time already meets the expectation. At this time, it is only necessary to maintain the CT value at the scan end time above the expected value CT E *. The formula derivation is as follows:

[0210] T D * = T* - Δt D * ------------------------------------------- Equation 1

[0211] T D = T 预延 + T D * ------------------------------------------ Equation 2

[0212] T TPS = T TP + Δt----------------------------------------Formula 3

[0213] CT TPS = CT TP + K1 × Δt--------------------------Formula 4

[0214] K2 = (CT E * - CT TPS ) / (T E * - T TPS )-------Formula 5

[0215] V 正式 = V 试验 + Q × Δt-----------------------------Formula 6

[0216] Integrate Formulas 1 and 2 to obtain the delay time in Case 2:

[0217] T D = T 预延 + T * - Δt D *

[0218] Integrate Formulas 3, 4, and 5 to obtain:

[0219] Δt = [CT E – CT TP – K2 × (T * - Δt D * + T S - T TP )] / (K1 - K2)------------------Formula 7

[0220] Integrate Formulas 6 and 7 to obtain the contrast agent dosage V during formal CT angiography 正式 .

[0221] 3. Calculation Method for Class III CT Angiography Parameters

[0222] 3.1 Overview of Class III Scheme

[0223] Class III CT angiography realizes the combined scanning of CT angiography of different vessels to be examined in a delayed staging manner. It can be used to achieve one-stop CT scans such as cerebral artery CTA + cerebral vein CTV, pulmonary artery CTA + left atrial CTV of pulmonary veins, CT scan evaluation of right atrium and ventricle + left atrium and ventricle, triple rule-out chest pain scan, and even whole heart and lung CT scan. Due to its staging scanning form, it can well handle the problem of excessive contrast agent usage in combined scanning. It realizes a new contrast agent bolus pretest method CT angiography technology with simple and practical operation, safe contrast agent flow rate, and reliable protocol calculation.

[0224] The function graph for calculating the formal angiography parameters by contrast agent bolus pretest is shown in ​ . The sampling points for combined scanning in the bolus pretest are shown in ​ .

[0225] 3.2 Analysis of Calculating Formal Scanning Parameters Based on the TDC Linear Function of Bolus Pretest in Class III CT Angiography

[0226] Combined with ​ the function graph for calculating in two-phase combined scanning, it can be seen that: for different vascular systems appearing within the monitoring layer of the contrast agent bolus pretest, through the type classification of Class I and Class II CT angiography, setting the expected enhancement value and phase suppression nodes in their respective blood vessels, and taking the scanning time of CT angiography of their respective vessels to be examined as preset, combined with the sampling calculation results of their respective contrast agent bolus pretests, the combination connection of two or more different CT angiographies is realized. The sequence of combined scanning of different CT angiographies is determined according to the delay time or forced delay time sequence obtained from the analysis results of the TDC of their respective contrast agent bolus pretests, and the contrast agent usage amount is the maximum value of the calculated results of the contrast agent usage amounts of each phase of angiography.

[0227] The formulas for each phase are summarized as follows:

[0228] T D强制 * = T D强制 –T 预延

[0229] The monitoring and discrimination formulas for the delayed scanning situation of each phase (N represents the sequence number of delayed staging):

[0230] CT D(K1)强制N * = CT TPN +K 1N ×(T D强制N *-Δt DN *-T TPN )

[0231] Situation 1:

[0232] When CT D(K1)强制N *≤CT DN*Time: Take the delay time determined by calculating the self-type (Type I or Type II) of the Nth-phase CT angiography, and the alternative contrast agent dosage is the calculation result of its corresponding classification situation.

[0233] Case 2:

[0234] When CT D(K1)强制N * > CT DN *Time: Take the mandatory minimum delay time T D强制 of the Nth-phase CT angiography as its delay time. At this time, the calculation formula for the alternative contrast agent dosage of this phase is as follows, and the result is used as a reference alternative, and finally the maximum value of each phase is taken: Δt N = [CT EN – CT TPN – K 2N × (T N * - Δt DN * + T SN - T TPN )] / (K 1N - K 2N ), V 正式N = V 试验 + Q × Δt N , and finally take the maximum value among the Vs 正式N of each phase as the final combined CT angiography formal contrast agent dosage.

[0235] The manual implementation methods of the above I-III class CT angiography parameter calculations are introduced as follows.

[0236] 1. Manual implementation method of I-class CT angiography parameter calculation

[0237] The manual operation of the I-class CT angiography Excel / WPS formula sheet is as ​ shown.

[0238] Manual operation process of the I-class formula sheet:

[0239] (1) Pre-enter the flow rate Q, the bolus pre-test contrast agent dosage V 测试 , the pre-test delay time T 预延 , the expected CT value CT D预期 *, CT E预期 *;

[0240] (2) Select the monitoring layer according to the location of the vessel to be examined, and perform a contrast agent saline bolus pre-test with sufficient contrast agent;

[0241] (3) Use the TDC analysis software to analyze the pre-test images, and manually input the data T1, CT1, T TP , CT TP, T2, CT2 to the corresponding positions in the formula table, and set the phase adjustment time Δt D *.

[0242] (4) According to the calculation results, delay the result column time T D Input to the CT host; for the contrast agent dosage V in the result column 正式 Take the integer part of the remainder, input it into the contrast agent dosage column for the formal scan of the high-pressure injector, and add the same amount of normal saline as in the pre-test.

[0243] (5) Perform a delayed exposure scan, and reconstruct and check the images.

[0244] 2. Manual implementation method for calculating II-class CT angiography parameters

[0245] Manually operate the II-class CT angiography Excel / WPS formula table as ​ shown.

[0246] Manual operation process of the II-class formula table:

[0247] (1) Pre-input the flow rate Q, bolus pre-test contrast agent dosage V 测试 , pre-test delay time T 预延 , expected CT value CT D预期 *, CT E预期 *;

[0248] (2) Select the monitoring layer according to the position of the blood vessel to be examined, and perform a bolus injection of contrast agent with normal saline for the pre-test with sufficient contrast agent;

[0249] (3) Use the TDC analysis software to analyze the pre-test images, and manually input the phase suppression time node information, sampling point 1 in the linear rising section, peak point, and sampling point 2 in the linear falling section data T*, CT*, T1, CT1, T TP , CT TP , T2, CT2 to the corresponding positions in the formula table, and set the phase adjustment time Δt D *;

[0250] (4) According to the calculation results, judge the monitoring calculation result CT D(K1) *(same as ​ CT in D(K1) ), after classifying the situation correctly, input the delay time T D in the delay time box of the CT host for the corresponding scheme result column; for the contrast agent dosage V in the result column 正式 take the integer part of the remainder, input it into the contrast agent dosage column for the formal scan of the high-pressure injector, and add the same amount of normal saline as in the pre-test;

[0251] (5) Perform a delayed exposure scan, and reconstruct and check the images.

[0252] 3. Manual implementation method for calculating parameters of Class III CT angiography

[0253] Manually operate the Class III CT angiography Excel / WPS formula sheet as ​ shown

[0254] Manual operation process of the Class III formula sheet (this is the two-phase combined scanning process, and the multi-phase operation method can be inferred by analogy):

[0255] (1) Pre-enter the flow rate Q, the amount of contrast agent used in the bolus pre-test V 测试 , the pre-test delay time T 预延 , the expected CT values CT D * A , CT E * A , CT D * B , CT E * B ;

[0256] (2) Select the monitoring layer according to the location of the blood vessel to be examined, and perform a contrast agent mixed with physiological saline bolus pre-test with sufficient contrast agent;

[0257] (3) Use the TDC analysis software to analyze the pre-test images, and manually input the ideal phase suppression time node information, sampling points in the linear ascending section, peak point, and sampling point data in the linear descending section of the two phases T A *, CT A *, T A1 , CT A1 , T TPA , CT TPA , T A2 , CT A2 , T B *, CT B *, T B1 , CT B1 , T TPB , CT TPB , T B2 , CT B2 to the corresponding positions in the formula sheet, and set the phase adjustment time Δt DA *, Δt DB *;

[0258] (4) Based on the calculation results, judge the monitoring calculation results CT D(K1)A * and CT D(K1)B *, after the situation classification is correct, transfer the delay times T DA , T DBEnter the delay time box of the corresponding stage of the CT host; the maximum contrast agent dosage in the two phase result columns is used as the formal scanning contrast agent dosage V 正式 Round off the remainder and enter it into the contrast agent dosage column of the high-pressure injector for the formal scan, and add the same amount of normal saline as in the pre-test;

[0259] (5) Perform phased time-lapse scanning and reconstruct and check the images.

[0260] Example 2

[0261] The calculation system of CT angiography parameters of the present invention comprises:

[0262] A point sampling unit is used to collect a peak point, at least one point on the rising segment, and at least one point on the falling segment from the TDC curve of the bolus injection pre-test, and obtain the CT value and time corresponding to each point;

[0263] The calculation unit is used to calculate the delay time and contrast agent dosage required for the formal scan based on the parameters collected by the sampling unit and the theory that for the formal scan, if the contrast agent is continuously injected at the same flow rate as the bolus injection pre-test, the concentration of the contrast agent at a certain position of the blood vessel will show an average CT value increase rate and decrease rate consistent with that in the small-dose test.

[0264] In a preferred embodiment, the CT angiography parameter calculation system further includes a vessel type selection unit for the operator to select the type of target vessel. Options include: Category I (CT angiography that is not easily interfered with by the display of a lower-level vessel), Category II (CT angiography that is easily interfered with by the display of a lower-level vessel), and Category III (staging combined CT angiography). Category I can be further divided into: cerebral vein CTV, carotid artery CTA, coronary artery CTA, thoracic and abdominal CTA, lower limb artery CTA, superior mesenteric artery CTA, portal vein CTV, and other CT angiography that is not easily interfered with by the display of a lower-level vessel. Category II can be further divided into: cerebral artery CTA, pulmonary artery CTA, other cerebral artery CTA, and other CT angiography that is easily interfered with by the display of a lower-level vessel. The vessel type selection unit is connected to the calculation unit and sends instructions to the calculation unit, instructing the calculation unit to calculate the delay time and contrast agent dosage required for the main scan using the corresponding method and formula based on the type of target vessel.

[0265] When the target vessel is Class I, the delay time and contrast agent dosage required for the formal scan are calculated using the following method and formula:

[0266] T D =T 预延 -Δt D *+T TP +(CT D *-CTTP ) / K1,

[0267] V 正式 =V 试验 +Q×Δt, where Δt = Δt 保底* +Δt 加持 , Δt 保底* =T D保底* -T TP , Δt 加持 =[CT E* -CT D* -K2×(T s -Δt D *)] / (K1 - K2), T D保底* =T TP +(CT D* -CT TP ) / K1;

[0268] When the target blood vessel is of type II, the delay time and contrast agent dosage required for the formal scan are calculated by the following method and formula:

[0269] Calculate the result of the monitoring and discrimination formula CT D(K1)* =CT TP +K1×(T* - Δt D *-T TP ), and compare it with the value of CT D *. If CT D(K1)* ≤CT D *, then T D =T 预延 -Δt D *+T TP +(CT D *-CT TP ) / K1, V 正式 =V 试验 +Q×Δt, where Δt = Δt 保底* +Δt 加持 , Δt 保底* =T D保底* -T TP , Δt 加持 =[CT E* -CT D* -K2×(T s -Δt D *)] / (K1 - K2), T D保底* =T TP +(CT D* -CT TP ) / K1; If CT D(K1)* >CT D *, then T D =T预延 +T * -Δt D *, V 正式 = V 试验 +Q×Δt, where Δt = [CT E –CT TP –K2×(T * -Δt D * + T S -T TP )] / (K1 - K2);

[0270] When the target blood vessel is of Class III, the delay time and contrast agent dosage required for formal scanning are calculated by the following method and formula:

[0271] Calculate the monitoring and discrimination formula CT for each phase of delayed scanning of Class III CT angiography D(K1)强制N * = CT TPN +K 1N ×(T D强制N * -Δt DN * -T TPN ) and compare the result with the value of CT DN *. If CT D(K1)强制N * ≤ CT DN *, select the delay time and contrast agent dosage alternative calculated for the corresponding classification of the Nth phase of CT angiography of its own type (Class I or Class II) as the calculation result for its corresponding classification; if CT D(K1)强制N * > CT DN *, select the mandatory minimum delay time T D强制 of the Nth phase of CT angiography as its delay time. At this time, the calculation formula for the alternative contrast agent dosage of this phase is as follows, and the result is used as a reference alternative, and finally the maximum value of each phase is taken: Δt N = [CT EN –CT TPN –K 2N ×(T N * -Δt DN * + T SN -T TPN )] / (K 1N -K 2N ), V 正式N = V 试验 +Q×Δt N , and finally select the maximum value of V 正式N in each phase as the final combined CT angiography formal contrast agent dosage.

[0272] The meanings of the above symbols are as shown in Table 1 of this specification.

[0273] Example 3

[0274] The CT scanning system of the present invention includes:

[0275] A CT scanning device for acquiring CT scan images;

[0276] A CT contrast agent for enhancing the visibility of CT scan images of a target blood vessel;

[0277] A processor for executing the CT angiography parameter calculation method of the present invention. The calculation method includes: based on the time-density curve of the region of interest obtained from the contrast agent bolus pretest, and based on the theory that for the formal scan, if the contrast agent is continuously injected at the same flow rate as in the bolus pretest, the concentration of the contrast agent at a certain position in the blood vessel will exhibit the same CT value rising rate and falling rate as in the small-dose test. By sampling points on the rising and falling segments of the time-density curve to calculate the CT value rising rate and falling rate, and combining the CT values and times of the sampled points and the CT value and time of the peak, the delay time and contrast agent dosage required for the formal scan of the region of interest are calculated.

[0278] In one embodiment, optionally, when sampling points on the rising and falling segments of the time-density curve to calculate the CT value rising rate and falling rate, at least two points are collected on the rising segment and at least two points are collected on the falling segment.

[0279] In one embodiment, optionally, the delay time and contrast agent dosage required for the formal scan are calculated by the following method and formula:

[0280] T D = T 预延 - Δt D * + T TP +(CT D *- CT TP ) / K1,

[0281] V 正式 = V 试验 + Q × Δt, where Δt = Δt 保底* + Δt 加持 , Δt 保底* = T D保底* - T TP , Δt 加持 =[CT E* - CT D* - K2 × (T s - Δt D *)] / (K1 - K2), T D保底* = T TP +(CT D* - CT TP ) / K1.

[0282] In one embodiment, optionally, different methods and formulas are used to calculate the delay time and contrast agent dosage required for the formal scan based on the type of the target blood vessel:

[0283] When the target vessel is Class I, T D =T 预延 -Δt D *+T TP +(CT D *-CT TP ) / K1,V 正式 =V 试验 +Q×Δt, where Δt=Δt 保底* +Δt 加持 , Δt 保底* =T D保底* -T TP , Δt 加持 =[CT E* -CT D* -K2×(T s -Δt D *)] / (K1-K2), T D保底* =T TP +(CT D* -CT TP ) / K1;

[0284] When the target vessel is Class II, the Class II CT angiography monitoring and identification formula is calculated. D(K1)* =CT TP +K1×(T*-Δt D *-T TP ) results, and CT D *Compare the values ​​such as CT D(K1)* ≤CT D *, then T D =T 预延 -Δt D *+T TP +(CT D *-CT TP ) / K1,V 正式 =V 试验 +Q×Δt, where Δt=Δt 保底* +Δt 加持 , Δt 保底* =T D保底* -T TP , Δt 加持 =[CT E* -CT D* -K2×(T s -Δt D *)] / (K1-K2), T D保底* =T TP+(CT D* -CT TP ) / K1; If CT D(K1)* >CT D *, then T D =T 预延 +T*-Δt D *, V 正式 =V 试验 +Q×Δt, where Δt=[CT E –CT TP –K2×(T*-Δt D *+T S -T TP )] / (K1-K2);

[0285] When the target blood vessel is of Class III, calculate the monitoring and discrimination formula for the delayed scan of each phase of the Class III CT angiography CT D(K1)强制N *=CT TPN +K 1N ×(T D强制N *-Δt DN *-T TPN ), and compare the result with the value of CT DN *. If CT D(K1)强制N *≤CT DN *, select the delay time and contrast agent dosage alternative calculated based on the self-type (Class I or Class II) of the Nth-phase CT angiography as the calculation result for its corresponding classification; If CT D(K1)强制N *>CT DN *, select the mandatory minimum delay time T D强制 of the Nth-phase CT angiography as its delay time. At this time, the calculation formula for the contrast agent alternative dosage of this phase is as follows, and the result is used as a reference alternative, and finally the maximum value of each phase is taken: Δt N =[CT EN –CT TPN –K 2N ×(T N *-Δt DN *+T SN -T TPN )] / (K 1N -K 2N ), V 正式N =V 试验 +Q×Δt N , and finally select the maximum value among the Vs 正式N of each phase as the formal contrast agent dosage for the final combined CT angiography;

[0286] The meanings of the symbols in the above formulas are as shown in Table 1 of this specification.

[0287] Those skilled in the art use the CT scanning system of the present invention for CT angiography, which mainly includes three steps: 1. Presetting condition parameters; 2. Analyzing and calculating the sampling points of the time-density curve through low-dose testing; 3. Inputting the contrast agent scheme parameters into the CT host scanning parameter setting interface and the high-pressure injector parameter setting interface, or automatically importing them into the CT host scanning program.

[0288] Example 4

[0289] This example provides cases of CT angiography using the calculation method of the CT angiography parameters of the present invention, which illustrate that high-quality scanned images can be obtained by performing CT angiography according to the method of the present invention.

[0290] Case 1: Cerebral artery CTA [II-class CT angiography]

[0291] Male, 58 years old, 175 cm, 70 kg. The monitored layers, monitoring points, and TDC curve sampling points are as ​ shown. Substitute each parameter into the formula, as ​ shown. The results of the monitored layers of the formal scanned images are as ​ shown. The comparison of the formal scanned images, the VRT and MIP three-dimensional reconstructions after fine-tuning the default window value, and the DSA examination results is as ​ shown.

[0292] Case 2: Carotid artery CTA [I-class angiography]

[0293] Female, 68 years old, 160 cm, 56 kg. The monitored layers, monitoring points, and TDC curve sampling points are as ​ shown. Substitute each parameter into the formula, as ​ shown. The results of the monitored layers of the formal scanned images are as ​ shown. The VRT of the formal scanned images with the default window value and the MIP three-dimensional reconstruction effect diagram with the appropriate window value are as ​ shown.

[0294] Case 3: Pulmonary artery CTA [II-class CT angiography]

[0295] Female, 82 years old, 163 cm, 75 kg. The monitored layers, monitoring points, and TDC curve sampling points are as ​ shown. Substitute each parameter into the formula, as ​ shown. The results of the monitored layers of the formal scanned images are as ​ shown. The formal scanned tomographic images and the VRT three-dimensional reconstruction effect diagram with the default window value are as ​ shown. The VRT three-dimensional reconstruction diagram after only cutting and the MIP diagram with the appropriate window value are as ​ shown.

[0296] Case 4: Coronary artery CTA of the heart [I-class CT angiography]

[0297] Male, 58 years old, 160 cm tall, 72 kg. Heart rate during pretest was 70 bpm, and heart rate during formal scan was 65 bpm. There was atherosclerotic plaque formation in the proximal segment of the right coronary artery, accompanied by mild stenosis of the lumen; there was mixed plaque formation in the proximal and middle segments of the left anterior descending artery, with mild stenosis of the lumen. The monitoring levels, monitoring points, and sampling points of the TDC curve are as ​ shown. Each parameter was substituted into the formula, as ​ shown. The new iodine flow rate used is as ​ shown. The results of the monitoring levels of the formal scan images are as ​ shown. The quality inspection of the formal scan tomographic images is as ​ shown. The three-dimensional post-processing effect diagram of the coronary artery is as ​ shown.

[0298] Case 5: CT Scanning Protocol for Preoperative Evaluation of Cardiovascular Radiofrequency Ablation and Left Atrial Appendage Occlusion by Double-Filling Pulmonary Vein Left Atrium CTV [Type I CT Angiography]

[0299] Female, 65 years old, 163 cm tall, 55 kg. Heart rate during pretest was 73 bpm, and heart rate during formal scan was 75 bpm. The monitoring levels, monitoring points, and sampling points of the TDC curve are as ​ shown. Each parameter was substituted into the formula, as ​ shown. The quality inspection of the formal scan tomographic images, and the results of double-filling at two-minute intervals are as ​ shown. The three-dimensional post-processing effect diagram of the formal scan images is as ​ shown.

[0300] Case 6: Thoracic Aortic CTA (with Part of the Abdominal Aorta) [Type I CT Angiography]

[0301] Male, 74 years old. The monitoring levels, monitoring points, and sampling points of the TDC curve are as ​ shown. Each parameter was substituted into the formula, as ​ shown. The results of the quality inspection of the formal scan tomographic images are as ​ shown. The three-dimensional reconstruction effect diagram of the default window value VRT is as ​ shown. The three-dimensional reconstruction effect diagrams of the sheared VRT and MIP are as ​ shown.

[0302] Case 7: CT Scanning Protocol for Pulmonary Artery CTA + Analysis of Right Atrial and Ventricular Diastolic & Systolic End Volume Index [Type II CT Angiography]

[0303] [[ID=​ As shown. Substitute each parameter into the formula, such as ​ As shown. The formal inspection results of the tomographic image quality are as ​ As shown. The three-dimensional effect diagram of the VRT post-processing without cutting the default window value is as ​ As shown. The three-dimensional post-processing diagram of the pulmonary artery VRT after cutting and adjusting the window value is as ​ As shown. The three-dimensional reconstruction of the right atrium and ventricle in diastole and systole volumes is as ​ As shown. Such as ​ Measurement results: The right ventricular end-diastolic volume index RVEDVI of this case is: 321.3 / (0.00607×176 + 0.0127×68 - 0.0698) = 172.55 ml / ㎡. The normal range of the right ventricular end-diastolic volume index is 60 - 100 ml / ㎡. Combining the echocardiogram measurement results, the pulmonary artery pressure value is 95 mmHg, and the patient's long-term COPD history, the severity of COPD is determined.

[0304] Case 8: Delayed staged cerebral vascular CT combined scan (cerebral artery CTA + cerebral vein CTV) [Class III CT angiography, combined structure: Class II + Class I (cerebral artery CTA and cerebral vein CTV belong to Class II and Class I CT angiography respectively)]

[0305] Male, 64 years old, 161 cm, 65 kg. The monitoring levels, monitoring points and TDC curve sampling points are as ​ As shown. Substitute each parameter into the formula, such as ​ Analysis: It can be seen that the delay time T* of the cerebral artery CTA is used as the reference for the phase suppression time, so 19.6 seconds is taken as the delay time of the cerebral artery phase; the normal delay of the cerebral vein CTV phase is 24 seconds, which is greater than the shortest mandatory delay of 23.6 seconds, so 24 seconds is taken as the delay time. Since the monitoring points of the cerebral vein phase and the cerebral artery phase are both in the neck, and the scanning direction of the cerebral vein CTV is from the top of the skull to the bottom of the skull, the starting expected value TD 预期 * is 290 HU (410 HU minus the heart rate compensation value of 120 HU), and the ending expected value is 570 HU (450 HU upper limit plus the heart rate compensation value of 120 HU). The contrast agent dosage in the arterial phase is 37.2 ml, and the dosage in the venous phase is 50 ml (rounding up the remainder of 49.3 ml in the venous phase). The contrast agent protocol is determined as: flow rate 5.0 ml / s, contrast agent injection volume 50 ml + normal saline 30 ml; the delay time of the cerebral artery CTA phase is 19.6 seconds; the delay time of the cerebral vein CTV phase is 24 seconds. The image verification results are as ​ As shown. The three-dimensional post-processing effect diagram of the VRT without cutting the default window value is as ​ As shown.

[0306] Case 9: CT Preoperative Evaluation Plan for Delayed Staged Cardiovascular Radiofrequency Ablation and Left Atrial Appendage Occlusion One-stop Surgery (Including Detection of Persistent Left Superior Vena Cava and Coronary Sinus Function of the Heart)

Class III CT Angiography, Structure II+I

[0307] Female, 69 years old, 150 cm tall, 50 kg. Heart rate: 70 bpm; An indwelling needle was inserted into the left elbow vein, and the procedure was the same as that for pulmonary artery CTA + pulmonary vein CTV. The sampling information of the monitoring points at the monitoring levels is as ​ shown. Each parameter was substituted into the formula, as ​ shown. Analysis: For the pulmonary artery CTA phase, the delay time was taken as 11.5 seconds for the Class II case 2 delay, and the delay time for the pulmonary vein left atrial CTV was the forced delay time of 27.1 seconds. The contrast agent dosage was taken as the dosage of 51 ml at the forced delay; After an interval of about 1 minute, the contrast agent was injected for the second time to fill the left atrium, and the delay time was 17.4 seconds, and the dosage was 32 ml. The total contrast agent dosage for this examination was 15 + 51 + 32 = 98 ml. The inspection results of the formal scanned images are as ​ shown. The three-dimensional post-processing effect diagrams are as ​ shown. The measurement data of the left atrial appendage occluder are as ​ shown. In Case 9, if the monitoring points of the second phase are placed at the coronary artery openings of the ascending aorta, the CT examination of the triple symptoms of chest pain with staged delayed scanning can be achieved.

[0308] Case 10: Delayed Staged Whole Heart and Lung CT Angiography Plan

Class III CT Angiography, Structure II+I

[0309] Female, 62 years old, 172 cm tall, 96 kg. Heart rate during testing was 72 bpm, and 69 bpm during formal scanning. The procedure was a combination of Case 7 + Case 5: Case 7 was used as the first phase, and Case 5 was used as the second phase. The first phase included the pulmonary artery, right atrium, and right ventricle, and the second phase included the pulmonary veins, left atrium, left ventricle, and coronary arteries. Both phases used electrocardiogram gating retrospective reconstruction coronary artery mode for staged delayed scanning. The sampling information of the monitoring points at the monitoring levels is as ​ shown. Each parameter was substituted into the formula, as ​ shown. The inspection results of the image quality are as ​ shown. Some of the three-dimensional reconstruction effect diagrams are as ​ shown.

[0310] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the method of the present invention, several improvements and supplements can still be made, and these improvements and supplements should also be regarded as the protection scope of the present invention.

Claims

1. A method for calculating CT angiography parameters, characterized in that, Including: Based on the time-density curve of the region of interest obtained from the contrast agent bolus pre-test, and based on the theory that for the formal scan, if the contrast agent is continuously injected at the same flow rate as in the bolus pre-test, the concentration of the contrast agent at a certain position in the blood vessel will show the same CT value rising rate and falling rate as in the small-dose test. By sampling points on the rising and falling segments of the time-density curve to calculate the CT value rising rate and falling rate, and combining the CT values and times of the sampled points and the CT values and times of the peak points, the delay time and contrast agent dosage required for the formal scan of the region of interest are calculated. The delay time and contrast agent dosage required for the formal scan are calculated by the following method and formula: T D = T 预延 - Δt D * + T TP + (CT D * - CT TP ) / K1 V_formal = V_test + Q × Δt Δt = Δt_guarantee* + Δt_enhancement Δt_guarantee* = TD_guarantee* - TTP Δt_enhancement = [CTE* - CTD* - K2 × (Ts - ΔtD*)] / (K1 - K2) TD_guarantee* = TTP + (CTD* - CTTP) / K1 When sampling points on the rising and falling segments of the time-density curve to calculate the CT value rising rate and falling rate, at least two points are collected on the rising segment and at least two points are collected on the falling segment. The delay time and contrast agent dosage required for the formal scan are calculated by the following method and formula: T D = T 预延 -Δt D * + T TP + (CT D * - CT TP ) / K1, V 正式 = V 试验 + Q × Δt, where Δt = Δt 保底* + Δt 加持 , Δt 保底* = T D保底 * -T TP , Δt 加持 = [CT E* - CT D* - K2 × (T s - Δt D *)] / (K1 - K2), T D保底 * = T TP + (CT D* - CT TP ) / K1; The meanings of the symbols in the above formula are as follows:

2. The calculation method according to claim 1, wherein According to the type of the target blood vessel: Type I: CT angiography that is not easily interfered with by the display of the next-level blood vessels for diagnosis. Type II: CT angiography that is easily interfered with by the display of the next-level blood vessels for diagnosis. Type III: Staged combined CT angiography; Different methods and formulas are used to calculate the delay time and contrast agent dosage required for the formal scan: When the target blood vessel is of Class I, then T D = T 预延 - Δt D * + T TP + (CT D * - CT TP ) / K1, V 正式 = V 试验 + Q × Δt, where Δt = Δt 保底* + Δt 加持 , Δt 保底* = T D保底 * - T TP , Δt 加持 = [CT E* - CT D* - K2 × (T s - Δt D *)] / (K1 - K2), T D保底 * = T TP + (CT D* - CT TP ) / K1; When the target blood vessel is of Class II, calculate the monitoring and discrimination formula CT of Class II CT angiography situation D(K1)* = CT TP + K1 × (T* - Δt D * - T TP ), and compare the result with the value of CT D *. If CT D(K1)* ≤ CT D *, then T D = T 预延 - Δt D * + T TP + (CT D * - CT TP ) / K1, V 正式 = V 试验 + Q × Δt, where Δt = Δt 保底* + Δt 加持 , Δt 保底* = T D保底* - T TP , Δt 加持 = [CT E* - CT D* - K2 × (T s - Δt D *)] / (K1 - K2), T D保底* = T TP + (CT D* - CT TP ) / K1; If CT D(K1)* > CT D *, then T D = T 预延 + T* - Δt D *, V 正式 = V 试验 + Q × Δt, where Δt = [CT E – CT TP – K2 × (T* - Δt D * + T S - T TP )] / (K1 - K2); When the target blood vessel is of Class III, calculate the monitoring and discrimination formula CT for the delayed scanning in each phase of the Class III CT angiography D(K1)强制N * = CT TPN + K 1N × (T D强制N * - Δt DN * - T TPN ), and compare the result with the value of CT DN *. If CT D(K1)强制N * ≤ CT DN *, select the delay time and the alternative contrast agent dosage calculated based on the self-type Class I or self-type Class II of the CT angiography in the Nth phase as the calculation results for their corresponding classification situations; if CT D(K1)强制N * > CT DN *, select the mandatory shortest delay time T D强制 of the CT angiography in the Nth phase as its delay time. At this time, the calculation formula for the alternative contrast agent dosage in the Nth phase is as follows, and the result is used as a reference alternative, and finally the maximum value of each phase is taken: Δt N = [CT EN – CT TPN – K 2N × (T N * - Δt DN * + T SN - T TPN )] / (K 1N - K 2N ), V 正式N = V 试验 + Q × Δt N , and finally take the maximum value among the Vs 正式N in each phase as the final combined CT angiography formal contrast agent dosage; The meanings of the symbols in the above formula are as follows:

3. A CT angiography parameter calculation system, characterized in that, Including: A sampling unit for sampling the peak point, at least one point on the rising segment, and at least one point on the falling segment from the TDC curve of the bolus pre-test, and obtaining the CT values and times corresponding to each point; A calculation unit for calculating the delay time and contrast agent dosage required for the formal scan based on the parameters collected by the sampling unit, and based on the theory that for the formal scan, if the contrast agent is continuously injected at the same flow rate as in the bolus pre-test, the concentration of the contrast agent at a certain position in the blood vessel will show the same average CT value rising rate and falling rate as in the small-dose test. The delay time and contrast agent dosage required for the formal scan are calculated by the following method and formula: T D = T 预延 -Δt D * + T TP +(CT D *-CT TP ) / K1 V_formal = V_test + Q × Δt Δt = Δt_guarantee* + Δt_enhancement Δt_guarantee* = TD_guarantee* - TTP Δt_enhancement = [CTE* - CTD* - K2 × (Ts - ΔtD*)] / (K1 - K2) TD_guarantee* = TTP + (CTD* - CTTP) / K1 The sampling unit samples at least two points on the rising segment and at least two points on the falling segment; The calculation unit calculates the delay time and contrast agent dosage required for the formal scan according to the following method and formula: T D = T 预延 - Δt D * + T TP + (CT D * - CT TP ) / K1, V 正式 = V 试验 + Q × Δt, where Δt = Δt 保底* + Δt 加持 , Δt 保底* = T D保底* - T TP , Δt 加持 = [CT E* - CT D* - K2 × (T s - Δt D *)] / (K1 - K2), T D保底* = T TP +(CT D* - CT TP ) / K1; The definitions of the symbols in the above formula are as follows:

4. The computing system according to claim 3, wherein The calculation system further includes a blood vessel type selection unit for selecting and determining the type of the target blood vessel, and the type of the target blood vessel includes: Type I: CT angiography that is not easily interfered with by the display of the next-level blood vessels for diagnosis. Class II: CT angiography that is easily interfered with by the display of the next-level blood vessels for diagnosis, Class III: Staging combined with CT angiography; The blood vessel type selection unit is further connected to the calculation unit and sends an instruction to the calculation unit to make the calculation unit calculate the delay time and contrast agent dosage required for the formal scan according to the type of the target blood vessel by using the corresponding method and formula: When the target blood vessel is of Class I, the delay time and contrast agent dosage required for the formal scan are calculated by the following method and formula: T D = T 预延 - Δt D * + T TP + (CT D * - CT TP ) / K1, V 正式 = V 试验 + Q × Δt, where Δt = Δt 保底* + Δt 加持 , Δt 保底* = T D保底* - T TP , Δt 加持 = [CT E* - CT D* - K2 × (T s - Δt D *)] / (K1 - K2), T D保底 * = T TP + (CT D* - CT TP ) / K1; When the target blood vessel is of Class II, the delay time and contrast agent dosage required for the formal scan are calculated by the following method and formula: Calculate the monitoring and discrimination formula CT for Class II CT angiography D(K1)* = CT TP + K1 × (T* - Δt D * - T TP ), and compare the result with the value of CT D *. If CT D(K1)* ≤ CT D *, then T D = T 预延 - Δt D * + T TP + (CT D * - CT TP ) / K1, V 正式 = V 试验 + Q × Δt, where Δt = Δt 保底* + Δt 加持 , Δt 保底* = T D保底 * - T TP , Δt 加持 = [CT E* - CT D* - K2 × (T s - Δt D *)] / (K1 - K2), T D保底* = T TP + (CT D* - CT TP ) / K1; If CT D(K1)* > CT D *, then T D = T 预延 + T* - Δt D *, V 正式 = V 试验 + Q × Δt, where Δt = [CT E – CT TP – K2 × (T* - Δt D * + T S - T TP )] / (K1 - K2); When the target blood vessel is of Class III, the delay time and contrast agent dosage required for the formal scan are calculated by the following methods and formulas: Calculate the monitoring and discrimination formula for the delayed scanning of each phase of Class III CT angiography CT D(K1)强制N * = CT TPN + K 1N × (T D强制N * - Δt DN * - T TPN ). Compare the result with the value of CT DN *. If CT D(K1)强制N * ≤ CT DN *, select the delay time and contrast agent dosage alternative calculated based on Class I or Class II of the CT angiography of its own type in the Nth phase of CT angiography as the calculation result of its corresponding classification; if CT D(K1)强制N * > CT DN *, select the mandatory minimum delay time T D强制 of the Nth phase of CT angiography as its delay time. The calculation formula for the contrast agent alternative dosage in this Nth phase is as follows, and the result is used as a reference alternative, and finally the maximum value of each phase is taken: Δt N = [CT EN – CT TPN – K 2N × (T N * - Δt DN * + T SN - T TPN )] / (K 1N - K 2N ), V 正式N = V 试验 + Q × Δt N . Finally, take the maximum value among the V 正式N of each phase as the final combined CT angiography formal contrast agent dosage; The meanings of the symbols in the above formula are as follows:

5. The computing system according to claim 4, wherein The Class I includes cerebral venous CTV, carotid artery CTA, coronary artery CTA, thoracic and abdominal CTA, lower extremity artery CTA, superior mesenteric artery CTA, and hepatic portal vein CTV; the Class II includes cerebral artery CTA and pulmonary artery CTA.

6. A CT scanning system, characterized in that, Including: A CT scanning device for obtaining CT scan images; A CT contrast agent for improving the display of the CT scan images of the target blood vessels; A processor for executing the method for calculating CT angiography parameters as described in claim 1 or 2.

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